Even the Black Death of the mid-fourteenth century, we are now being told, practised racial discrimination as it raged through Europe wiping out maybe half of the existing population. The new idea is that black people were more likely to die from the plague than white ones. The ‘evidence’ presented by an American researcher and an employee of the Museum of London consists of skull measurements where there are said to be signs of black ancestry; it is not derived from DNA, which would be much more comprehensive. Many of the bones of Black Death victims come from the Crossrail tunnels, so as you approach Liverpool street on the Elizabeth Line you are passing under what were once plague pits in which the bodies of victims were unceremoniously buried.

Modern political obsessions derived from Critical Race Theory now determine the past

Really, though, this is not about evidence at all. It is about ideology: the assumption, a far-fetched one, is that late medieval London teemed with people of very varied ethnic origins who had arrived from far away. And the assertion, which is without any foundation whatsoever, is that they were mainly servants, often female, and therefore subject to ‘white oppression’, living off a poorer diet than white Londoners and therefore showing less resistance to disease.

The argument does not seem to be that certain ethnicities are more prone genetically to certain diseases, such as sickle-cell anaemia. The fact that the random sample of crania studied is tiny (nine bodies attributed to black plague victims) makes this so-called scientific research laughable. Studying skulls, admittedly according to a different technique, was a favourite exercise of racial theorists in the Nazi era, who fanatically measured Jewish heads to prove that Jews are a distinct and subhuman species different from Aryan mankind. The museum of Las Palmas on Gran Canaria has rooms full of medieval skulls which were supposed to show that the native inhabitants of the island were pure exemplars of ‘Cro-Magnon Man’, which was useful for Franco’s claim that the Canary islanders had always been part of the equally Cro-Magnon Spanish race, even before their conquest in the fifteenth century. In reality, skull shape is determined by many factors, including childhood diet and age of puberty; and the time of the Black Death (1347-51) was an age when famine often struck and malnutrition was common.

Ah, you will say, but what about all those English folk with the name Black? Isn’t that proof of black ancestry going back many centuries? No: much more probably the name records descent from a blacksmith, or from someone with black hair, or – scandalously – a Black Friar from the Dominican Order who gave way to temptation. By the time of the Black Death (which will obviously have to be renamed) an occasional sailor who was an ex-slave of African origin could have arrived in London aboard a Genoese or Catalan ship, because there were routes linking the western Mediterranean, with its active slave trade, to England. But in medieval Italy African slaves were described as ‘olivastre’,  olive-skinned, or even described as white, just as the Berbers of north Africa are olive-skinned or white to this day.

The problem with these supposed revelations goes much deeper. Modern political obsessions derived from Critical Race Theory now determine the past. It is no longer a case of what happened but of what one wants to think happened. And that is determined by what is misleadingly called the pursuit of Social Justice. Cases of this sort of self-deception in describing the past abound. A key moment in the origins of the Industrial Revolution has come under the spotlight. Controversial assertions about the origins of Henry Cort’s innovative methods of iron-production – now being attributed to Caribbean slaves of West African origin from whom he supposedly stole the technique – has shown how gaps in the evidence can be creatively filled by unwarranted speculation, and bits of evidence can be (if the critics are correct, as they seem to be) misread. But this and other such research is being conducted in support of a higher objective, such as the payment of reparations or the promotion of twisted conceptions of ‘Equality, Diversity and Inclusion’.

That does not mean that every fantasy about the past is motivated by activist ideology. Leading scholars can fall victim to bizarre fantasies. My favourite example is the insistence of a distinguished expert on the Dead Sea Scrolls, the late John Allegro, that Jesus was actually a mushroom (or at any rate a hallucination produced by magic mushrooms). The problem is often that people begin with an idea, for instance, that the rebel Perkin Warbeck really was the son of King Edward IV, and then insist on reading the evidence with the sole intention of proving this. That is not how historians should work. The evidence needs to be studied before, not after, the argument is definitively framed. The real identity of Perkin Warbeck is not going to shake any political foundations after 500 years, but there are sinister aspects to the way the past is being misused, bound up with cranky but dangerous conspiracy theories like Holocaust denial, and latterly the denial that the murderous attack by Hamas on Israel took place on 7 October. In the debate about Henry Cort we are being told that it is an exercise of white supremacy to argue that ‘facts are facts’. The good thing is that, as these cases arise, it becomes more and more obvious that this way of studying the past is intellectually bankrupt and that it is time to return to the aims and standards of traditional history-writing.